1. Field of the Invention
The present invention pertains to the filling of oxygen cylinders and, more particularly, to a gauge block assembly for transfilling of high pressure gaseous oxygen cylinders.
2. Description of the Prior Art
In the medical industry gaseous oxygen contained within high pressure cylinders is frequently utilized. These cylinders come in a variety of sizes and shapes. Because of the durable construction of the cylinder tanks, it is not practical, from an economic or monetary viewpoint, to simply dispose of the cylinders when the oxygen within them has been exhausted.
Instead of disposing of the cylinders, the cylinders may be refilled with gaseous oxygen. In order to refill the cylinders, it is first necessary to empty or evacuate any remaining or residual oxygen and/or contaminants from the cylinder. This is accomplished by applying a vacuum to the interior of the cylinder and drawing out the remaining contents. Once this is complete, a partial vacuum exists inside the cylinder. The now empty cylinder is then refilled with fresh oxygen under a predetermined pressure.
Because of the nature and use of oxygen contained within high pressure cylinders, the refilling of such cylinders with oxygen is regulated by the Food and Drug Administration (FDA). One aspect regulated by the FDA is the filling rate of the high pressure oxygen cylinders. A cylinder will heat as it is filled from a high pressure source. The more rapidly the cylinder is filled, the higher the temperature will rise in the cylinder due to the heat of compression. Excessive temperatures may result in the ignition of any combustibles that may be present, as well as causing structural damage to the cylinders, which can undermine the integrity of the cylinders. FDA regulations thus set forth a maximum incoming gaseous flow rate for refilling of the cylinders. This flow rate cannot be exceeded.
The full flow cylinder pressures generally fall within 2K-3K PSIG. However, although the FDA regulations state that the cylinders must be evacuated to at least 25 inches (635 MM) of mercury, at seal level, the evacuation flow rate is not a regulated aspect. Thus, the evacuation process may transpire unrestricted, flowing at the maximum rate of the totally open flow valve, while the filling process is restricted to a maximum flow rate.
In view of the FDA regulations, prior art regulators for gas flow control in the refilling of high pressure oxygen cylinders utilize a restricted straight through orifice. This is the gas flow path for both the evacuation and refilling processes. Because this is the case, the orifice is thus sized to permit the maximum rate of gaseous flow into the cylinder as allowed by FDA regulations for refilling. This however, also limits the evacuation flow rate. Thus, although the evacuation flow rate is not regulated by the FDA and may therefore transpire at any rate, the use by prior art devices of a restricted orifice for both evacuation and refilling in order to adhere to the FDA regulations setting the maximum refilling flow rate, increases the overall time it takes to complete the entire refill process.
The evacuation time for three "E" type high pressure cylinders utilizing prior art restricted orifices is found to be approximately 12.5 minutes. Also, the overall process includes refilling the cylinders with oxygen, which would double the time for completing the entire process. Thus, very few cylinders may be refilled in a given period of time.
There is thus a need for decreasing the total overall time necessary to complete the entire refilling process in order to be able to process more cylinders in a given period of time.
It is thus an object of the present invention to decrease the overall time necessary to evacuate and refill a high pressure cylinder with oxygen.
It is therefore an object of the present invention to provide a gauge block assembly for the oxygen transfill process that increases the evacuation flow rate so as to decrease the total evacuation time, while also not exceeding the maximum fill rate established by regulation.